Abrasive articles, such as fixed, coated and bonded abrasive articles, are used in various industries to abrade work pieces by hand or by machine processes, such as by lapping, grinding, or polishing. Machining utilizing abrasive articles spans a wide industrial and consumer scope from optics industries, automotive paint repair industries, and metal fabrication industries to construction and carpentry. Machining, whether using complex automated systems or by hand with commonly available tools, such as with orbital polishers (both random and fixed axis), and belt and vibratory sanders, is performed to remove surface material in an amount, and in a manner, that achieves desirable surface characteristics.
Surface characteristics can include, among others, shine, texture, gloss, surface roughness, and uniformity. In particular, surface characteristics, such as roughness, gloss, and lack of surface imperfections are measured to determine quality. For example, when coating or painting a surface certain imperfections or surface defects can occur during the coating application or coating curing process. Such surface imperfections or surface defects might include pock marks, “orange peel” texture, “fish eyes”, encapsulated bubbles, and dust defects, a.k.a., “dust nibs.” Typically, such defects in a painted surface are removed by first sanding with a coarse grain abrasive, followed by subsequently sanding with progressively finer grain abrasives, and even buffing with wool or foam pads until a desired smoothness is achieved. Hence, the properties of an abrasive article used will generally influence the surface quality.
In addition to surface characteristics, industries are sensitive to cost related to abrasive operations. Factors influencing operational costs include the speed at which a surface can be prepared and the cost of the materials used to prepare that surface. Typically, the industry seeks cost effective materials having high material removal rates.
However, abrasives that exhibit high removal rates often exhibit poor performance in achieving desirable surface characteristics. Conversely, abrasives that produce desirable surface characteristics often have low material removal rates. For this reason, preparation of a surface is often a multi-step process using various grades of abrasive sheets. Typically, surface flaws (e.g., scratches) introduced by one step are repaired (e.g., removed) using progressively finer grain abrasives in one or more subsequent steps. Therefore, abrasives that introduce scratches and surface flaws result in increased time, effort, and expenditure of materials in subsequent processing steps and an overall increase in total processing costs.
An additional factor affecting material removal rate and surface quality is the “loading” of the abrasive with “swarf”, i.e., the material that is abraded from the workpiece surface, which tends to accumulate on the surface of, and between, the abrasive particles. Loading is undesirable because it typically reduces the effectiveness of the abrasive product and can also negatively affect surface characteristics by increasing the likelihood of scratching defects.
The surface characteristics and material removal rate can also be affected by the durability of the abrasive article. Abrasive articles that wear easily or lose grains can exhibit both a low material removal rate and can cause surface defects. Quick wear on the abrasive article can lead to a reduction in material removal rate, resulting in frequent exchanging of the abrasive article and increased waste associated with discarded abrasive articles.
There continues to be a demand for improved abrasive articles.
The use of the same reference symbols in different drawings indicates similar or identical items.